Quarterly report pursuant to Section 13 or 15(d)

Stock-based compensation - Narrative (Details)

v3.5.0.2
Stock-based compensation - Narrative (Details) - USD ($)
1 Months Ended 3 Months Ended 6 Months Ended
Oct. 31, 2013
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Options outstanding (in shares)   2,626,512   2,626,512   1,672,578
Stock-based compensation       $ 379,928 $ 504,400  
Stock Options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Unrecognized compensation cost related to unvested stock-based awards   $ 2,300,000   $ 2,300,000    
Unrecognized compensation cost, recognition period       3 years 11 months 1 day    
Options granted, weighted-average grant date fair value (in dollars per share)   $ 1.38   $ 1.07    
Stock Options | General and Administrative Expense            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock-based compensation   $ 235,961 $ 326,400 $ 379,928 $ 504,400  
Restricted Stock            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Options outstanding (in shares)   761,250   761,250   0
The 2013 Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Authorized shares (in shares) 4,773,992          
Contractual term 10 years          
Award vesting period 5 years